Method for unattended sealing of tubing

ABSTRACT

A clip on welder includes two pairs of opposed grippers defined by pivotally attached upper and lower frames for latching the welder to heat weldable material, such as a length of tubing, upon actuation of a start button by an operator; thereafter, the welder operates unattended. At least a jaw of a pair of jaws disposed intermediate the two pairs of grippers heats the material compressed and lodged therebetween to form a weld in or across the material. A source of gas, such as air, under pressure selectively connected to a bellows provides the power to pivot the upper and lower frames into gripping engagement with the material. A source of electrical signals provides the power to heat the material intermediate the pair of jaws. One or more thermocouples senses the heat of the jaws and generates signals used to control the application of power and to control cooling. After completion of the weld, cooling air is directed to the jaws until the thermocouple(s) signal(s) indicates a sufficiently low temperature. Release of the welder from the material is in response to actuation of a stop button by the operator.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a division of and claims priority to anapplication entitled “CLIP ON THERMAL WELDER”, filed Mar. 12, 2004,assigned Ser. No. 10/799,106, now U.S. Pat. No. ______, whichapplication is directed to an invention made by the present inventorsand assigned to the present assignee.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to tubing welders and, more particularly,to clip on unattended welders for forming a seal in a length of tubingto seal the tubing.

2. Description of Related Art

It is well known that plastic materials may be welded to one another bythe application of heat. Many prior art devices developed for thispurpose are essentially immobile units particularly adapted for massproduction requirements in a manufacturing facility.

As suggested above, plastic materials may be welded to one another byapplication of heat. Numerous devices have been developed for thispurpose of which the following descriptions are representative. U.S.Pat. No. 2,529,717 describes an RF energized heat sealer wherein oneelectrode of a pair of electrodes is removable to accommodate placementof the material to be sealed between the electrodes; a constant RFenergy level is applied for a timed duration to effect the seal. U.S.Pat. No. 2,629,809 is directed to a manually operated device forcompressing thermoplastic material between an anvil and a hammerwhereupon RF energy is applied until the hammer has been raised to apredetermined height. U.S. Pat. No. 2,751,965 illustrates a bag sealeremploying a first timing circuit for maintaining compressed the openingof the bag intermediate electrodes and a second timing circuit forapplying a fixed level of RF energy. U.S. Pat. No. 3,040,153 illustratesa yarn splicer having a pair of pinchers for compressing yarn endsintermediate fixed position electrodes between which RF energy istransmitted to fuse the yarn ends to one another. U.S. Pat. No.3,232,810 illustrates the use of a tuned cavity to regulate thetransmission of RF energy for sealing polyester materials. U.S. Pat. No.3,518,396 is directed to a series of resonant circuits which precludethe work piece from altering the heat distribution pattern of adielectric heating apparatus. U.S. Pat. No. 3,632,943 describes adielectric heat sealer which incorporates a liquid filled coil as acooling medium to ensure uniformity of the seals; shield means are alsoemployed to prevent spurious RF leakage. U.S. Pat. No. 3,738,892illustrates two spaced apart conductive members for inductively heatingand welding two adjacent sheets of plastic to one another without anattendant compression of the sheets.

There is a continual existing need for blood donors in order to meet theday to day hospital demands for blood. Consequently, many privateorganizations, whether or not affiliated with hospitals, have arisen forthe sole purpose of collecting blood. In order to obtain sufficientquantities of blood, these organizations must visit locations having ahigh concentration of blood donors. That is, they must periodicallyvisit schools, office buildings, factories and the like and they musttransport all equipment necessary to collect the donated blood.

Normally, the blood is drawn from a donor through flexible tubingextending into a plastic bag. Once the bag is filled to its capacity,the tubing must be sealed to prevent leakage and, more importantly,prevent deterioration of the collected blood. Because of the requiredmobility and rapid processing of a blood collection unit, any and allequipment required must be specifically designed for compact storage,minimum reliance upon support facilities at the blood collectionlocation, minimum operating and set up times and ease of operability.

Plastic tubing, particularly of the type used in conjunction with thecollection of blood, is relatively fragile and is easily burst whenheated to a temperature close to its melting point. To effectively andrepetitively accurately heat seal or weld such tubing, certainparameters must be observed. The heat applied should be limited to theheat necessary to effect a weld. The locality of the applied heat shouldbe focused upon the actual physical section upon which the weld is to bemade to preclude softening of adjacent material as such softening maypermit the fluid, under pressure within the tubing, to burst the tubing.

To meet the need for readily and easily sealing blood filled plastictubing, a hand held operated tubing sealer has been developed and isdescribed in U.S. Pat. No. 4,013,860 entitled “Hand HeldElectromechanical Sealer”, assigned to the present assignee andincorporated herein by reference. This sealer is a readily transportablesealer of small size and is hand operated to form heat seals in anyplastic tubing placed intermediate its jaws. Thus, it is readily usableto form seals at the donor site prior to withdrawing the needle andmaintaining a sterile closed system. Also, a plurality of sealedsegregated compartments along a length of tubing filled with blood canbe completed, wherein each of the compartments is identified with acommon serial number. Thereafter, the compartments may be segregatedfrom one another and various tests may be preformed upon the sample ofblood contained in the compartments. This capability is particularlyimportant where testing is necessary and yet maintenance of the seal forthe blood within the attendant collection bag is not to be disrupted orbroken.

At most blood collection centers, such as those operated by the RedCross, much of the manual labor is performed as charitable work by olderpersons. These persons are physically handicapped by the naturalprocesses of aging, by arthritis or by previous injuries. For thosepersons whose hands are not strong or who suffer pain when they attemptto grip an article with their hands, a hand held sealer is difficult orpainful to use. Consequently, the rate of production of seals isessentially slower than optimum. A desk mounted sealer described in U.S.Pat. No. 4,186,292, assigned to the present assignee and incorporatedherein by reference, is usable by an operator who is either seated orstanding and it provides a direct line of sight for the operator ineither position. Thereby, operator fatigue is diminished and accuratepositioning of the liquid filled tubing to be automatically sealed ispromoted. Through actuation of a tubing position sensing switch or afoot operated switch, a seal will be effected in the tubing placedintermediate a fixed and a movable jaw, thereby allowing the operator touse one or both hands to repetitively place and reposition the tubingintermediate the jaws. The housing for the sealer sealingly encloses theoperative elements to preclude seepage of fluid thereinto from a burstliquid filled length of tubing. The shaft supporting the moveable jawand extending from within the housing is sealed through a wiping seal.The jaws themselves and the attendant structure are developed from largemass heat conducting material to dissipate the heat generated by thejaws and to preclude heat build up for the benefit of both the operatorand the integrity of the formed seals.

U.S. Pat. No. 4,390,832, assigned to the present assignee andincorporated herein by reference, describes an RF generating circuit forproviding a source of RF energy to seal a length of tubing placedintermediate a pair of jaws. The pair of jaws are electrically connectedto the source of RF energy as plates of a variable capacitor in an RFresonant circuit. The flow of RF energy across the pair of jaws, whichenergy heats the tubing and, in conjunction with mechanical pressure,makes the weld, is a function of timing and of the spacing between thejaws, which spacing affects the degree of resonance of the RF resonantcircuit. Simultaneous with the heating of the tubing, the configurationof the pair of jaws compresses the tubing placed therebetween andfocuses the RF energy in a narrow swath across the tubing whilesimultaneously elongating and spreading the tubing at the swath toobtain a leak free weld. The resulting weld is configured to provide forseparation of the sealed compartments of the tubing without tearing orrupturing the compartments.

In U.S. Pat. No. 4,529,859, assigned to the present assignee andincorporated herein by reference, a solenoid operated moveable jaw isdisclosed which cooperates with a fixed jaw protruding from a bloodtubing sealing unit and formed as part of a relatively massive heat sinkto effect seals on liquid filled plastic tubing upon transmission of RFenergy timed to coincide with a degree of initial mechanical compressionof the tubing by the jaws after the movement of the moveable jaw hasbeen triggered by the tubing intercepting and reflecting a beam oflight. Dissipation of heat from the exposed parts of the fixed jaw is byconvention. Dissipation of heat from the enclosed part of the fixed endmoveable jaws and that produced by the circuitry generating the RFenergy internal to the sealer unit is effected by channeling the heat byconduction from all internal heat sources to the bottom and rear platesof the unit and dissipating the heat from the bottom and rear plates tothe atmosphere by convection.

U.S. Pat. No. 5,750,971, assigned to the present assignee andincorporated herein by reference, discloses the use of RF power formelting, sealing and welding plastic tubing compressed between a pairmanually or automatically actuated electrically conducting jaws of ahand held or fixed base tubing sealer. The RF power is regulated by apulse width modulator controlling the duty cycle of applied constantvoltage pulses. A predetermined change of impedance of the tubing duringcompression and melting is detected to regulate the power applied and toensure a weld of predetermined physical parameters. On completion of theweld, a first timer is reset and a further weld may be made. In theevent of impedance mismatch, a second timer inhibits further applicationof power and resetting of the first timer. The use of the pulse widthmodulator enhances conservation of the power and accommodatesportability of the tubing sealer through use of rechargeable batteriesas the power source.

Each of the tubing sealers described or referenced above, requireattendance by an operator during the sealing process. Depending upon thesize and material of the tubing to be sealed as well as the rate andlevel of power applied to effect heating to form the weld, each weld maytake tens of seconds or in excess of a minute. At blood collectioncenters, the use of hand held or desk mounted tubing sealers requiresthe attendance of an operator for the duration of the seal(s) to bemade. For efficiency purposes and to simultaneously harvest as muchcollected blood as possible from as many donors as possible whileengaging as few operators as possible, elimination of operator time toeffect a seal(s) is desirable as such an operator can attend to othermatters while a seal(s) is being formed.

SUMMARY OF THE INVENTION

A clip on welder includes two pairs of opposed grippers defined bypivotally attached upper and lower frames for latching the welder to alength of tubing. By pushing a start button an operator will cause abellows to inflate in response to air flow from a source of compressedair to force the frames to pivot relative to one another and bring twopairs of grippers into latching engagement with the tubing. At least ajaw of a pair of jaws disposed intermediate the two pairs of grippersthereafter heats the tubing compressed and lodged therebetween to form aweld across the tubing. A source of electrical signals actuated by theoperator pushing the start button provides the power to heat the jawswhich heat the tubing intermediate the pair of jaws.

One or more thermocouples associated with the jaws sense the heat of thejaws and generate signals used by a programmed controller to controlapplication of power to the jaws. After a specified temperature has beenreached for a period of time, commensurate with the formation of a weld,power to the jaws is terminated. Thereafter, cooling air from a sourceof compressed air is directed to the jaws to cool them until a specifiedreduced temperature is reached. The bellows will remain inflated and thewelder latched to the tubing until an operator depresses a stop buttonand thereby permit exhausting the air form the bellows.

It is therefore a primary object of the present invention to provide awelder for welding a heat weldable material while unattended by anoperator.

Another object of the present invention is to provide a welderattachable to and supported by the heat weldable material to be weldedand without attention of an operator during the welding process.

Still another object of the present invention is to provide a tubingwelder for forming a weld in tubing which welder may be attached to andremoved from a length of the tubing at the convenience of an operatorand without requiring attendance by the operator during formation of theweld.

Yet another object of the present invention is to provide a clip ontubing welder that requires minimal instruction on the operation of thewelder.

A further object of the present invention is to provide a clip on welderthat may incorporate any of various heat generating elements to form aseal across a length of tubing placed between a pair of jaws.

A still further object of the present invention is to provide a clip ontubing welder to form a seal unattended by an operator and toautomatically cool the heated jaws upon completion of the seal.

A yet further object of the present invention is to provide a method forforming a weld in a heat weldable material while unattended by anoperator.

A yet further object of the present invention is to provide a method forattaching a welder to and supporting the welder from heat weldablematerial that is to be welded and during formation of the weld.

A yet further object of the present invention is to provide a method foreffecting a seal across a length of tubing with a clip on tubing welderthat operates unattended to form the seal and subsequently cool theoperative elements.

These and other objects of the present invention will become apparent tothose skilled in the art as the description thereon proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with greater specificity andclarity with reference to the following drawings, in which:

FIG. 1 illustrates the clip on welder coupled to a housing having asource of air under pressure and a source of electrical signals foroperating the welder;

FIG. 2 is similar to FIG. 1 but certain components have been removed;

FIG. 3 is an exploded view of the welder with certain components removedtherefrom;

FIG. 3A is an enlarged view of the structure within circle 3A shown inFIG. 3;

FIG. 4 illustrates the interior of the bottom frame of the welder;

FIG. 5 illustrates the interior of the top frame of the welder;

FIG. 6 is top view of the welder;

FIG. 7 is a cross sectional view of the welder taken along lines 7-7, asshown in FIG. 6;

FIG. 8 is an end view of the front of the welder;

FIG. 9 is a bottom view of the welder;

FIG. 10 is a partial cross sectional view taken along lines 10-10, asshown in FIG. 9;

FIG. 11 is a partial cross sectional view taken along lines 11-11, asshown in FIG. 9; and

FIG. 12 is a schematic of the welder and its operative components.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a tubing welder assembly 10 forperforming a seal across a heat weldable length of tubing. The assemblyincludes a clip on welder 12 engaging a representative length of tubing14 engaged thereby, as illustrated. A support housing 16 contains asource of a gas, such as air, under pressure (not shown) and a source ofelectrical signals (not shown). The gas under pressure is conveyedthrough a plurality of pneumatic conduits enveloped within a sleeve 18to welder 12. A plurality of electrical signals are conveyed from withinhousing 16 through a cable 20 to the welder. After the welder has beenbrought into engagement with tubing 14, as illustrated, a start button22 is depressed. On actuation of the start button, the tubing will begripped by the welder to support the welder and permit unattendedoperation of the welder during formation of the weld across the tubingto form a seal. On completion of the weld, the element(s) providing therequisite heat are deactivated and the element(s) are cooled by a flowof air. At some point thereafter, an operator would depress stop button24 to permit disengagement of the welder from the tubing. Thus, theoperation of welder 12 requires operator involvement only to the extentof attaching and detaching the welder from the tubing.

While the above discussion is a summary of the preferred embodiment,variations thereof can be made without departing from the spirit andscope of the invention. For example, the welder will work in conjunctionwith any heat weldable tubing irrespective of size and wall thickness orwhether the tubing is empty or filled with blood (as it might be used ina blood collection center). Other fluids of any type can also be presentwithin the tubing during formation of a weld. The welder is notrestricted to use with tubing. It will form a weld unattended by anoperator upon any heat weldable material, whether it be a sheet, a film,or other physical configuration. The type, nature, size andconfiguration of the weld is a function of the commensurateconfiguration of the jaw or jaws used to heat the heat weldable materialand the nature of the type of energy applied to heat the heat weldablematerial. For example, two or more sections of material may be welded toone another to join them or to form a compartment therebetween or otherdelineation. And, it is possible to weld together heat weldablematerials of different physical configurations by correspondingadaptations of the jaws to be energized.

FIG. 2 is similar to FIG. 1 except that the housing is missing alongwith sleeve 18 enveloping the pneumatic conduits. As illustrated, apneumatic fitting 26 includes three hollow prongs 28 for engagement withrespective sources of air pressure within housing 16. The air pressureattendant each of these prongs is conveyed through three pneumaticconduits 30, 32 and 34 to welder 12. Similarly, electrical plug 36interconnects a plurality of electrical conductors within cable 20.

As particularly shown in FIG. 3, upper frame 38 and lower frame 40 arepivotally attached to one another by a shaft 42 engaging apertured ears44, 46 of upper frame 38 and mating ears (of which ear 48 is shown) oflower frame 40. Conduits 30, 32 covey a flow of air on command to coolthe heating elements on completion of the weld, as will be described infurther detail below. Conduit 34 conveys a flow of air to a pneumaticfitting 52 in fluid communication with a bellows to be described (seeFIG. 3A). A cover plate 54 is detachably attached to lower frame 40 topermit access to the pneumatic conduits entering the welder; preferably,the cover plate is hollowed to accommodate the conduits and the fittingand suitably notched to permit passage of the conduits.

FIG. 4 illustrates the components interior to lower frame 40. Asdiscussed above, ears 48, 50 pivotally engage ears 44, 46 in upper frame38 via shaft 42. A conduit 32 conveys a flow of air to a passagewaypartly surrounding electrode 62, which electrode envelops heatingelement 64 of jaw 68. The electrode is embedded within a ceramic jawholder 66, as will be described in further detail below. Pneumaticconduit 32 is in fluid communication with the corresponding componentsin upper frame 38. A pair of grippers 70, 72 are disposed on opposedsides of holder 66. Each of these grippers includes an oval likedepression or the depression may be circular but defining less than halfa circle; the two depressions are identified by numerals 74, 76corresponding with grippers 70, 72, respectively. Gripper 70 alsoincludes a pair of flats 70A, 70B disposed on opposed sides ofdepression 74. Gripper 72 includes similar flats 72A, 72B. Asrepresentatively shown, a length of tubing 14 is supported by thedepressions in grippers 70, 72. As shown in FIG. 5, upper frame 38includes a gripper 106 having a depression 108 and flats 106A and 106Bextending from the depression. Similarly, gripper 110 includes adepression 112 and flats 110A and 110B extending from the depression.

Referring to FIG. 5, further components interior of upper frame 38 areillustrated. Cable 20 includes a plurality of electrical conductors forconveying power and the requisite control signals to the componentswithin the upper frame. In particular, conductors 80, 82 go to switch 84corresponding with start button 22. Conductors 86, 88 go to switch 90corresponding with stop button 24. Conductors 92, 94 go to heatingelement 96 of jaw 97 disposed within electrode 98 of jaw holder 100.Conductors 102, 104 go to heating element 64 (see FIG. 4) in lower frame40. Additionally, electrical conductors (not shown) exist within cable20 that interconnect circuitry within housing 16 with thermocouples orother temperature/heat sensing devices that may be used to sense thetemperature/heat of the heating elements and/or jaws to be describedbelow. A bar 116 depends from the base of upper frame 38 for cooperativeengagement with a similar bar 114 supported by bellows 60 (see FIG. 4).

Referring jointly to FIGS. 6, 7 and 8, additional structural elementsand their relationships to one another will be described. Heatingelement 64 includes a thermocouple 120 lodged therein or adjacentthereto to sense the temperature of the heating element and/or the jaw.It is connected to circuitry within housing 16 by an electricalconductor 122. Similarly, heating element 96 includes a thermocouple 124for the purpose of sensing the temperature of the heating element and/orthe jaw; it is also connected to electrical circuitry within housing 16by an electrical conductor 126. These thermocouples or othertemperature/heat sensing devices may be differently located inconjunction with either or both jaws in the alternative or in addition.Thereby, the temperature of the heating elements (and/or jaws) isdeterminable during operation of the heating elements. Shut off of powerto the heating elements, once a predetermined temperature is reached ormaintained for a specified period of time, will occur by operation ofthe circuitry within housing 16 (see FIGS. 1 and 12). The shut offtemperature in combination with duration at a specified temperature is afunction of the material of the tubing to be welded.

Bellows 60 includes bar 114 which is extended upon inflation of thebellows to bear against bar 116 and cause pivotal movement of upper andlower frames relative to one another to urge electrodes 62, 98 (jaws 68,97) toward one another causing compression of the tubing disposedtherebetween and flatten the tubing to place the opposed inside surfacesadjacent another. Simultaneously, the two pairs of grippers in the upperand lower frames engage the tubing disposed therein to grip the tubingand thereby attach or latch welder 12 to the tubing.

Upon expansion of bellows 60, the resulting upward movement of bar 114and bearing against bar 116 will cause the upper and lowers frames topivot with respect to one another. Grippers 70, 72 in lower frame 40 andgrippers 110, 106 in upper frame 38 will be repositioned toward oneanother an amount sufficient to grip the tubing disposed in thecorresponding depressions. As the tubing will become squeezed, it willexpand laterally. To accommodate such expansion, flats 70A, 70B arespaced apart from flats 110A, 110B and flats 72A, 72B are spaced apartfrom flats 106A, 106B. Electrode 62 (jaw 68) will become located adistance from electrode 98 (jaw 97) essentially equivalent to andpreferably somewhat less than twice the wall thickness of the tubingbeing welded. This limited travel is controlled by wall sections 142,144 in upper frame 38 coming in contact with wall sections 146, 148 inlower frame 40, respectively, as shown in FIGS. 4 and 5.

Referring jointly to FIGS. 9, 10 and 11, features attendant thepneumatic operation of welder 12 will be described. Pneumatic conduit 30is attached to an hollow barb 130 defining a passageway 134 to providefluid communication with a passageway 132 partly surrounding electrode62 encasing heating element 64. Passageway 132 extends forwardly toexhaust the air flowing therethrough at the front of the welder.Similarly, pneumatic conduit 32 is connected to an hollow barb having apassageway 136 to provide a flow of air to passageway 138 surroundingelectrode 98 and embedded heating element 96 (jaw), which passagewayalso exhausts air at the front of the welder. Thereby, after a weld hasbeen performed, the electrodes and their heating elements (Jaws) arecooled by the air flow. Upon termination of the weld, any lingering heatfrom the electrodes will not compromise the weld made.

FIG. 11 illustrates, in dashed lines, extension of bellows 60 upon aninflow of air from passageway 140 in fitting 52. As illustrated, bar 114is in engagement with bar 116 and will cause pivotal movement of theupper and lower frames relative to one another.

FIG. 12 is a schematic of the operative and functional elements ofwelder 12 and housing 16. Housing 16 includes a programable controller150 for controlling generation of various electrical signals necessaryfor operation of welder 12; the electrical conductors therefor arerepresentatively identified by numeral 20. In addition, it controlsoperation of the pneumatic system for pivoting the upper and lowerframes of the welder and for providing controlled air flow to theelectrodes; the pneumatic conduits therefor are representativelyidentified by numeral 18. A source 152 of electrical power, whether itbe a portable battery or conventional house current, provides therequisite electrical power to the programable controller. Similarly, asource 154 of compressed air provides compressed air to a set of valves156. It may be noted that a gas other than air may be used. Theprogramable controller provides electrical power to each of heatingelements 64, 96 through pairs of electrical conductors 158, 160.Electrical conductors 122, 126 are in communication with the respectivethermocouples lodged in conjunction with heating elements 64, 96,respectively, and provide indicia responsive to the temperature of therespective heating elements. The sensed temperatures provide an input tothe control circuitry of the programmable controller to bring abouttermination of power to the heating elements once the requisite andpredetermined temperature has been reached and/or maintained for apredetermined time period. These conductors are within cable 20, asdiscussed above. Valve 162 is an electrically actuated valve forselectively conveying air from source 152 into conduit 164 in responseto a control signal transmitted via conductor 166. As representativelyshown and identified as a pneumatic actuator, bellows 60 (describedabove) will inflate in response to a flow of air through conduit 164. Oncompletion of the weld, a valve 168 is actuated to provide a flow of airfrom source 154 through conduit 170 to exhaust air into the passagewaysin each of the jaws, as described above. This valve is controlled bysignals transmitted from the programable controller through conductor172. When the programable controller senses, through the signalsgenerated by the thermocouples, that the jaws are sufficiently cooled,valve 168 is closed and further cooling air flow will not occur. Uponactuation of stop button 24, valve 162 will release the air pressurewithin conduit 164 and the bellows will collapse. Thereafter, the jawsof the upper and lower frames may be manually (or under urging of aspring or the like) separated from one another to permit withdrawal ofthe tubing disposed therebetween.

In the present embodiment, each of the heating elements is a simpleresistive cartridge heater commercially available in the market place.However, numerous other devices could be used to cause heating of thetubing to be welded between the jaws, including RF energy (as describedabove in certain of the assignee's patents), inductive heating, sonicheating or radiant heating. Moreover, the power provided may be AC, DCor radiant energy.

While the presently contemplated primary use of the present inventionrelates to heat weldable tubing of any of many types of chemicalcompositions, other forms of heat weldable materials could be welded.These forms may be bags to be sealed, segregation of chambers betweensheets of material, etc.

1. A method for unattended sealing of tubing with a clip on welder, saidmethod comprising the steps of: a) clipping the welder at two spacedapart locations on a length of the tubing to be sealed; b) energizing atleast one jaw for heating and melting the tubing to form a sealintermediate the two locations; c) providing a source of gas underpressure on command to practice said step of clipping; d) furtherproviding a source of electrical signals to effectuate said step ofenergizing; and e) unclipping the welder from the length of tubing oncompletion of the seal.
 2. The method as set forth in claim 1 whereinthe at least one jaw includes a pair of opposed jaws and said step ofclipping includes the step of moving the jaws toward one another tocompress the tubing therebetween.
 3. The method as set forth in claim 2including the step of limiting movement of the jaws to a spaced apartdistance equivalent to no more than twice the wall thickness of thetubing being compressed.
 4. The method as set forth in claim 1 includingthe step of cooling the jaws on completion of the seal, said step ofcooling including the step of forcing air through a passageway in atleast one of the jaws and exhausting the air from the passageway to theatmosphere.
 5. The method as set forth in claim 1 including the step ofsensing the temperature of at least one jaw and the step of controllingthe heating of the tubing as a function of the temperature sensed. 6.The method as set forth in claim 1 wherein the welder includes an upperand a lower frame pivotally interconnected and wherein said step ofclipping and said step of unclipping includes the step of pivoting theupper and lower frames relative to one another.
 7. The method as setforth in claim 6 including the step of inflating and deflating a bellowsto exercise said steps of clipping and unclipping.
 8. The method as setforth in claim 7 wherein said step of clipping includes the step ofgripping the tubing at two spaced apart locations.
 9. The method as setforth in claim 1 including a programmable controller for exercising eachof the steps of clipping, energizing, providing, further providing andunclipping.
 10. The method as set forth in claim 1 including the step ofthermally insulating each of the jaws from adjacent elements.